Master Switches

Just finished a panel upgrade on a Normal category (Not Experimental). One change made was to use PowerFlarm for GPS logging and glide computer. My master switch is a 3 position switch (Bat 1, Off, Batt 2). My old Volkslogger had no problem with swtching batteries as long as I flipped the switch fast, If I was slow it would reboot. Can I expect the same from the PF? I was thinking of wiring both batteries to one master or having two battery switches. I see no reason to use one battery at a time.
I bought the ship recently and it has much of the original electrical wiring and hardware (looks straight out of a German Home Depot). I initially purchased factory replacement electrical parts but they are expensive and not of very high quality. I wish to switch to Mil-Spec or higher quality for the master switch(S). Any recommendations? Discussed this with my IA and he has no problem with non factory stuff as long as it is aircraft grade (Which my sentiment also).
Thanks in advance.
Kirk

Craggy Aero and others have the wire (Tefzel), switches & breakers you'll need. Call Richard there for help. There are a couple of schools of thought on how to configure batteries. A-off-B versus separate switches as you suggested. The experts will clarify more.

On Saturday, April 20, 2013 1:22:49 PM UTC-7, K wrote:
Just finished a panel upgrade on a Normal category (Not Experimental). One change made was to use PowerFlarm for GPS logging and glide computer. My master switch is a 3 position switch (Bat 1, Off, Batt 2). My old Volkslogger had no problem with swtching batteries as long as I flipped the switch fast, If I was slow it would reboot. Can I expect the same from the PF? I was thinking of wiring both batteries to one master or having two battery switches. I see no reason to use one battery at a time.

I bought the ship recently and it has much of the original electrical wiring and hardware (looks straight out of a German Home Depot). I initially purchased factory replacement electrical parts but they are expensive and not of very high quality. I wish to switch to Mil-Spec or higher quality for the master switch(S). Any recommendations? Discussed this with my IA and he has no problem with non factory stuff as long as it is aircraft grade (Which my sentiment also).
, now
Thanks in advance.

Kirk

I have used 2 separate master switches (one for each battery)for years. If you hook both batteries together in parallel, you will need to charge both batteries after each flight. I use my primary (12a/h) until I get a low voltage warning on my SN-10, then switch to my backup 7a/h. This happens at about the 3 hour mark. I turn on the second battery and then turn off the first battery to prevent even a slight voltage gap. Please, no posts talking about voltage spikes, I have tested that and got something like 120 m/a flow as the new battery briefly tried to 'charge' the old battery and no voltage spike!
JJ

We recently put a re-paneled Duo Discus into service with a Clear Nav and CN vario (which I like a lot). We discovered the type of switch you have (ON-OFF-ON) would re-start the ClearNav no matter how quickly it was flipped. We have gone to a switch for each battery and the protocol is to turn on the subsequent switch before turning off the first one. No problems.

wrote:
We recently put a re-paneled Duo Discus into service with a Clear Nav and
CN vario (which I like a lot). We discovered the type of switch you have
(ON-OFF-ON) would re-start the ClearNav no matter how quickly it was
flipped. We have gone to a switch for each battery and the protocol is
to turn on the subsequent switch before turning off the first one. No problems.

Now keep in mind that I am a software guy and know just enough about
electronics to be dangerous, but couldn't you just wire in a sufficiently
large capacitor to bridge the temporary loss of power? I seem to remember
something like that in the wiring instructions for my Volkslogger.

Pete

On Monday, April 22, 2013 4:32:03 PM UTC-7, vontresc wrote:
wrote:

We recently put a re-paneled Duo Discus into service with a Clear Nav and

CN vario (which I like a lot). We discovered the type of switch you have

(ON-OFF-ON) would re-start the ClearNav no matter how quickly it was

flipped. We have gone to a switch for each battery and the protocol is

to turn on the subsequent switch before turning off the first one. No problems.



Now keep in mind that I am a software guy and know just enough about

electronics to be dangerous, but couldn't you just wire in a sufficiently

large capacitor to bridge the temporary loss of power? I seem to remember

something like that in the wiring instructions for my Volkslogger.



Pete

Not sure why folks want to make this complicated. I've been doing it JJ's way and it's rock simple and works flawlessly. Time spent with both batteries in parallel is minimal.

Cheers,
Craig

Agree, two switches and parallel the batteries for as long as you need. It really doesn't matter much.
The NKK toggle switches which require pulling out to unlock before you can change position seem the best. I've bought them from Mouser.com.
The SPST is Mouser part# 633-M2011LL3W03
NKK part# M2011LL3W03
(hopefully that's correct, I'm on Mouser's antipodal site at the moment)
Or search locking toggle switch spst
They make them in SPDT, DP, On/Off/On, etc.
Jim

In article K writes:
Just finished a panel upgrade on a Normal category (Not Experimental). One =
change made was to use PowerFlarm for GPS logging and glide computer. My ma=
ster switch is a 3 position switch (Bat 1, Off, Batt 2). My old Volkslogger=
had no problem with swtching batteries as long as I flipped the switch fas=
t, If I was slow it would reboot. Can I expect the same from the PF? I was =
thinking of wiring both batteries to one master or having two battery switc=
hes. I see no reason to use one battery at a time.

I would suggest that there is an advantage to using both batteries together,
all the time.

If you buy a pair new from a good source, they should have the same capacity
and discharge curve. Connect them both together (with a fuse at the positive
terminal of each battery, just in case), then run that to your single master
switch.

This will give you a longer total run time than using them individually,
as the lower discharge rate will provide more energy before the battery is
discharged. (Or, it will discharge them by a lower percentage of charge
for a given flight time resulting in a longer lifetime for the batteries.)

For example, the common 7 AH battery used in many gliders will provide
..35 amps for 20 hours, or .7 amps for a bit over 8 hours.

If you run them one at a time, you get .7 amps for about 17 hours.

If you parallel two of these, they each provide .35 amps for 20 hours, so
you get a total of .7 amps for 20 hours.

When the charge does start to get lower, your current peaks will be split
between the two batteries, so you should get less voltage drop (such as when
you transmit).

To do this, use a good low resistance connection between the batteries,
on both positive and negative terminals. You want the current to come from
both equally, so it would be best to connect your lead to the master to a
midpoint of that connection (as well as the lead to airframe ground).

Notes:

Safety: Some caution needed if connecting in the aircraft that the second
positive doesn't touch the airframe while not yet connected. For this reason,
connect both positives first, then both negatives; disconnect negative (ground)
first, then the positives. That way, a positive touching airframe metal won't
short things.

Charge the batteries together. Ideally, you can avoid the above safety note
and have the harness between them be permanent, so they charge as a pair, again
with lead lengths balanced.

Alan

If your batteries are dissimilarly discharged during flight (which is
possibly the reason you want to switch batteries) then the instantaneous
current flowing through your circuit when you join them could be quite high
and cause you more problems.

There are two better ways to solve this problem:

1) Insert a capacitor across the power as has been suggested. A further
enhancement would be a choke across the switch.

2) Power your loggers etc off a separate bus which is connected through a
rectifier bridge to both batteries. The logger will draw power from the
higher voltage battery and neither battery can charge the other. There will
be a voltage drop of between 0.5 and 1 volt but most loggers will work down
to 9v so no problem.

Jim

ps: avoid thermal trips if voltage loss is an issue.

I'm setting up a way to switch between each battery independently versus two or three batteries slaved together via the use of a simple circuit of diodes (rectifiers) and capacitors. The switches we all use are break before make so you don't want to lose power to instruments when switching between batteries. I found a suitable rotary mini-switch with up to 6 positions so you can do any combination of batteries you like (individually or slaved together). I realize the diodes cost about 0.15 volts on the output side so being able to get a little extra juice might be better but I also discovered that batteries last longer if you don't regularly deep discharge them. Since I have two main batteries in the baggage area plus one in the tail I figure my main scenario will be to slave the two mains together via diodes so theres no cross-charging and each draws down at half the rate. On a typical day they only get halfway drained and keep the tail battery as a fallback. I don't want to take the tail off to recharge the tail battery every day. This means I need a switch to go between Batt 1, Batt 2, Batt 1+2 and Batt 3. A position for Batt 1+2+3 is an option, but not super attractive if you wan an emergency reserve.

I've been using around 2500 micro farads of capacitor with a 1 ohm power resistor across the leads for several years. Works great.In v2 I'm upping the capacitance.

9B

On Tuesday, April 23, 2013 1:06:58 AM UTC-7, Jim White wrote:
If your batteries are dissimilarly discharged during flight (which is

possibly the reason you want to switch batteries) then the instantaneous

current flowing through your circuit when you join them could be quite high

and cause you more problems.



There are two better ways to solve this problem:



1) Insert a capacitor across the power as has been suggested. A further

enhancement would be a choke across the switch.



2) Power your loggers etc off a separate bus which is connected through a

rectifier bridge to both batteries. The logger will draw power from the

higher voltage battery and neither battery can charge the other. There will

be a voltage drop of between 0.5 and 1 volt but most loggers will work down

to 9v so no problem.



Jim



ps: avoid thermal trips if voltage loss is an issue.